Description of the Prior Art
In the past, braiding machines have been of two basic types, one in which bobbins have been guided to move in sinusoidal, overlapping paths which creates the braid and the other in which the bobbins move counter-directionally on counter-rotating tables and braid strand guide elements or fingers are used to move the strands of the outer bobbin array over and under the strands of the inner bobbin array to create the braiding action. In each type of braider, the structural requirements are stringent since, if the apparatus is to be economically useful, it should be capable of operating at productive speeds. Obviously as the operating speed of such machines is increased, the engineering problems also increase and at a faster rate than does machine speed. The problems associated with moving relatively large masses at high speed means that tight machine tolerances are necessary and that all moving and driving elements should be under positive control at all times.
There exist in the prior art examples of that class of braiders in which braid strand guides are used in conjunction with the strands of the outer bobbins. Marrog U.S. Pat. No. 2,672,071 which issued 3/16/54 describes the such example.
In this Marrog patent, the braid strand is fed from a plurality of bobbins 16 which are carried on the outer table 10 that is arranged to move in counter-rotation with respect to the upper or inner table 11. The strand 19 which comes from bobbin 16 is fed upwardly around a plurality of guiding rollers and finally, through a housing 24. Mounted on the housing 24 is a guide tube 27 through which the strand 19 exits in the manner clearly shown in FIGS. 3 and 4 of the drawings. In order to move the strands 19 alternately over and under the strands 17, it is necessary that the guide tubes 27 be moved in an oscillating fashion about the axis of the outer housings 24. This is accomplished by means of a ball joint 33 and a link 32 which is attached to the guide tube 27 in the fashion shown. The other end of links 32 are connected to cam followers 34. The cam followers ride in a slot 35 in the cylindrical cam plate 36. Thus it can be seen that as the cam follower 34 travels in the cam path 35 the guide tube 27 will be moved alternately above and below the inner bobbins 14 which carry the inner strands 17. In this arrangement it is quite clear that the length of the strand 19 coming from the guide tube 27 and going to the braid point remains substantially constant, this being a feature which is required if strand tension is to be maintained constant between the guide tube and the braid point.
While the Marrog apparatus does manage to keep the strand tension substantially constant between the strand exit and the braid point, the manner in which the guide tubes are oscillated limits the speed at which operation can be effected. Because the cam follower 54 must contact different sides of cam track during the path of travel, this restricts the speed of operation because the cam follower is not under positive control at all times and excessive increase in speed will cause severe vibration to be initiated.
A second example of that class of machines which utilizes strand guide fingers in conjunction with the outer array of bobbins may be found by referring to the Sokol U.S. Pat. Nos. 2,464,899 and 3,892,161. In each instance here the outer strand is guided over and under the inner strands by means of guide fingers which move radially inwardly and outwardly with respect to the axis of rotation of the machine tables. This is a less than desirable condition because the length of the strand varies with respect to the braid point and when the strand length varies in this fashion tension cannot be maintained constant.
It is therefore a principal object of this invention to provide an improved braiding machine of the type in which the outer strands are controlled and can be operated successfully at high speeds while maintaining constant strand tension.
Another object of this invention is to provide a strand guide system for a vertical braiding machine which is at all times positively driven.
A further object of this invention is to provide a strand guide system for a vertical braiding machine which is simple, rugged and thereby permits higher operating speeds than was heretofore possible.
Yet another object of this invention is to provide a strand guide system for the outer strands of a vertical braider in which a guide finger is operatively connected to a cam/cam follower drive means that maintain positive control over the finger at all times.